1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
|
<HTML
><HEAD
><TITLE
>CD-ROMs</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.7"><LINK
REL="HOME"
TITLE="The Linux System Administrator's Guide"
HREF="index.html"><LINK
REL="UP"
TITLE="Using Disks and Other Storage Media"
HREF="c973.html"><LINK
REL="PREVIOUS"
TITLE="Floppies"
HREF="x1060.html"><LINK
REL="NEXT"
TITLE="Tapes"
HREF="x1092.html"></HEAD
><BODY
CLASS="sect1"
BGCOLOR="#FFFFFF"
TEXT="#000000"
LINK="#0000FF"
VLINK="#840084"
ALINK="#0000FF"
><DIV
CLASS="NAVHEADER"
><TABLE
SUMMARY="Header navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TH
COLSPAN="3"
ALIGN="center"
>The Linux System Administrator's Guide: </TH
></TR
><TR
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="bottom"
><A
HREF="x1060.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="80%"
ALIGN="center"
VALIGN="bottom"
>Chapter 6. Using Disks and Other Storage Media</TD
><TD
WIDTH="10%"
ALIGN="right"
VALIGN="bottom"
><A
HREF="x1092.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="AEN1075"
></A
>6.4. CD-ROMs</H1
><P
>A CD-ROM drive uses an optically read, plastic coated disk.
The information is recorded on the surface of the disk
<A
NAME="AEN1078"
HREF="#FTN.AEN1078"
><SPAN
CLASS="footnote"
>[1]</SPAN
></A
>
in small `holes' aligned along a spiral from the center to the edge.
The drive directs a laser beam along the spiral to read the disk.
When the laser hits a hole, the laser is reflected in one way; when
it hits smooth surface, it is reflected in another way. This makes
it easy to code bits, and therefore information. The rest is easy,
mere mechanics.</P
><P
>CD-ROM drives are slow compared to hard disks. Whereas a
typical hard disk will have an average seek time less than 15
milliseconds, a fast CD-ROM drive can use tenths of a second for
seeks. The actual data transfer rate is fairly high at hundreds of
kilobytes per second. The slowness means that CD-ROM drives are not
as pleasant to use as hard disks (some Linux distributions provide
`live' filesystems on CD-ROMs, making it unnecessary to copy the
files to the hard disk, making installation easier and saving a lot
of hard disk space), although it is still possible. For installing
new software, CD-ROMs are very good, since maximum speed is not
essential during installation.</P
><P
>There are several ways to arrange data on a CD-ROM. The most
popular one is specified by the international standard ISO 9660.
This standard specifies a very minimal filesystem, which is even
more crude than the one MS-DOS uses. On the other hand, it is so
minimal that every operating system should be able to map it to its
native system.</P
><P
>For normal UNIX use, the ISO 9660 filesystem is not usable, so
an extension to the standard has been developed, called the Rock
Ridge extension. Rock Ridge allows longer filenames, symbolic
links, and a lot of other goodies, making a CD-ROM look more or less
like any contemporary UNIX filesystem. Even better, a Rock Ridge
filesystem is still a valid ISO 9660 filesystem, making it usable by
non-UNIX systems as well. Linux supports both ISO 9660 and the Rock
Ridge extensions; the extensions are recognized and used
automatically.</P
><P
>The filesystem is only half the battle, however. Most CD-ROMs
contain data that requires a special program to access, and most of
these programs do not run under Linux (except, possibly, under
dosemu, the Linux MS-DOS emulator, or wine, the Windows emulator.
<A
NAME="AEN1084"
HREF="#FTN.AEN1084"
><SPAN
CLASS="footnote"
>[2]</SPAN
></A
>
There is also VMWare, a commercial product which emulates an
entire x86 machine in software
<A
NAME="AEN1088"
HREF="#FTN.AEN1088"
><SPAN
CLASS="footnote"
>[3]</SPAN
></A
>)
.</P
><P
>A CD-ROM drive is accessed via the corresponding device file.
There are several ways to connect a CD-ROM drive to the computer:
via SCSI, via a sound card, or via EIDE. The hardware hacking
needed to do this is outside the scope of this book, but the
type of connection decides the device file.</P
></DIV
><H3
CLASS="FOOTNOTES"
>Notes</H3
><TABLE
BORDER="0"
CLASS="FOOTNOTES"
WIDTH="100%"
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
WIDTH="5%"
><A
NAME="FTN.AEN1078"
HREF="x1075.html#AEN1078"
><SPAN
CLASS="footnote"
>[1]</SPAN
></A
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
WIDTH="95%"
><P
>That is, the surface inside the disk, on
the metal disk inside the plastic coating.</P
></TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
WIDTH="5%"
><A
NAME="FTN.AEN1084"
HREF="x1075.html#AEN1084"
><SPAN
CLASS="footnote"
>[2]</SPAN
></A
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
WIDTH="95%"
><P
>Ironically perhaps, wine actually stands
for <SPAN
CLASS="QUOTE"
>"Wine Is Not an Emulator"</SPAN
>. Wine, more strictly, is an
API (Application Program Interface) replacement. Please see
the wine documentation at <A
HREF="http://www.winehq.com"
TARGET="_top"
>http://www.winehq.com</A
>
for more information.</P
></TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
WIDTH="5%"
><A
NAME="FTN.AEN1088"
HREF="x1075.html#AEN1088"
><SPAN
CLASS="footnote"
>[3]</SPAN
></A
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
WIDTH="95%"
><P
>See the VMWare website, <A
HREF="http://www.vmware.com"
TARGET="_top"
>http://www.vmware.com</A
>
for more information.</P
></TD
></TR
></TABLE
><DIV
CLASS="NAVFOOTER"
><HR
ALIGN="LEFT"
WIDTH="100%"><TABLE
SUMMARY="Footer navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
><A
HREF="x1060.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="index.html"
ACCESSKEY="H"
>Home</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
><A
HREF="x1092.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>Floppies</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="c973.html"
ACCESSKEY="U"
>Up</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>Tapes</TD
></TR
></TABLE
></DIV
></BODY
></HTML
>
|
